The present disclosure relates generally to pull-up riser tensioner systems used on offshore floating production and drilling platforms and, more particularly, to improved methods and systems for connecting a riser tensioner system to a riser.
Offshore production platforms are often used when performing offshore subterranean operations. Such offshore platforms must typically support a riser that extends from the platform to a subsea well. In some instances, the offshore platform may be fixed to ocean floor, thereby readily providing support for the riser as is known in the art. However, in certain deep water implementations using floating platforms such as tension leg platforms or semi-submersible platforms, supporting the risers may prove challenging. Specifically, a floating platform may move up and down or may be displaced horizontally due to oscillations from waves and currents. It is desirable to maintain a predetermined tension on the riser despite the platform oscillations. Accordingly, tensioners are often utilized to maintain a desired tension on the riser as the platform oscillates.
FIG. 1 depicts a typical riser tensioner system in accordance with the prior art. As shown in FIG. 1, a typical pull-up riser tensioner system 100 may include multiple tensioner cylinders 102. In certain implementations, the tensioner cylinders 102 may be hydro-pneumatic cylinders. A lower distal end of the tensioner cylinders 102 may be coupled to a threaded tension ring 104 disposed on a riser 106. As used herein, the term “riser” may refer to both production and drilling risers. The opposite, top distal end of the tensioner cylinders 102 is coupled to the platform structure 108 either directly or through another frame such as a cassette. Accordingly, the tensioner cylinders 102 serve to maintain a substantially constant tension on the riser 106 as the floating platform 108 moves vertically or horizontally due to wind, waves, and other natural events. The tensioner cylinders 102 serve as the connection between the tension ring 104 on the riser 106 and the floating platform 108.
The tensioner cylinders 102 are usually installed on the platform 108 prior to running the riser 106. Accordingly, one of the final steps in running the riser 106 is to couple the riser 106 to the tensioner cylinders 102 and transfer the riser weight from the rig to the tensioners. Typically each tensioner cylinders 102 is connected to the tension ring 104 by a shackle or a pin and bearing connection 110. In order to make that connection, rig personnel are required to manually align each tensioner cylinder 102 individually with the tension ring 104 and secure the shackle or pin in place. However, the current approaches for coupling the tensioner cylinders 102 to the tension ring 104 have a number of drawbacks. For instance, when using the pin and bearing design, there must be a precise alignment between the tensioner cylinders 102 and the tension ring 104 due to tight tolerances. Similarly, the shackles used in tensioner systems weigh over 300 pounds making them difficult to handle with limited to no crane access. Accordingly, the current approach for coupling tensioner cylinders 102 to the tension ring 104 requires rig personnel working in tight spaces and a hazardous environment over the water and handling heavy pins and shackles. It is therefore desirable to develop a more efficient approach for coupling tensioner cylinders to the tension ring on a riser.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.